This invention relates to hinges and collapsible containers in general, and specifically to an improved collapsible container.
In the materials handling and other industries, it can be beneficial to use collapsible containers to transport and store objects and materials. Among other things, such containers can be erected to hold things in a relatively secure manner during transport or storage, and can be collapsed during non-use to minimize the space occupied by the container. Commonly, such containers are provided in reusable, stackable configurations, to further improve their usefulness. An example of containers of this type is illustrated in U.S. Pat. No. 4,917,255 to Foy et al. Drawings from that patent are included herein as FIGS. 1-8, to illustrate certain aspects of prior art containers.
In a common application for such containers, the containers are erected and filled with parts to be used (for example) on an assembly line. A plurality of erected containers are stacked atop one another and loaded into a semi-trailer, which transports them to the location of the assembly line. Upon arrival there, the containers are positioned beside the assembly line adjacent the location at which the parts are to be used. Once a container is emptied of parts, it is collapsed and set aside. The collapsed containers can be gathered together and returned to the parts supplier (or to another supplier) in the collapsed state, where the entire cycle can then be repeated.
In such an application, it is beneficial for such containers to have a high "return ratio". This ratio is the number of collapsed containers that occupies the same space as one erected container. The name "return ratio" is thus apparently derived from an application such as the foregoing, in which the focus is on "returning" the maximum number of collapsed containers (to eventually be refilled by the parts supplier) in the smallest space. By returning a greater number of containers in a given space, the number of shipments required to transport the empty, collapsed containers is thereby reduced. Correspondingly, the amount of space required to store the empty, collapsed containers is reduced, both before and after shipment. Thus, collapsible containers with a relatively high return ratio (current "good" ratios are currently typically 3:1) are in many applications more economical to use and store than are containers with lower return ratios.
In addition, however, the efficiency, speed, quality and profitability of many applications (including those similar to the aforementioned assembly line application) can be improved by simplifying the processes and time required to erect and collapse the containers. To the extent that the containers can be collapsed by the assembly line workers without a great deal of physical effort or mental concentration, the workers can instead focus that effort and concentration on the actual assembly work (hopefully improving that work product). A common configuration which allows rapid erection and collapse is a rectangular or square base and four interlocking sidewalls, each hinged to a side of the base so that the sidewalls fold over the base into a parallel, stacked relationship.
In many prior art containers of this type, these two factors (return ratio versus speed or efficiency) have been a tradeoff. For example, when the required or desired height of the erect container is more than half the width of the container base, and when the walls are hinged to the base along a hinge line near the base itself, opposing pairs of walls cannot be collapsed without overlapping each other. This problem has been resolved in prior art containers in two primary ways, each exemplifying a different balance of the two factors.
In the first approach, each hinge line is raised away from the base. This is done by integrally molding onto the edge of the base what is equivalent to a portion of the erected sidewall. Because it is integrally molded and is not hinged but is instead fixed to the base, this portion cannot be collapsed, and it therefore typically makes the collapsed container taller than it otherwise might be (it reduces the "return ratio" because it spaces the collapsed walls away from the base). Because it reduces the height of the foldable portion of the sidewall, however, it permits the sidewalls to be folded in a relatively simple manner (without overlapping). In other words, moving the hinge line up the side of the container makes it easier to collapse the container (because the collapsed wall portions do not overlap and therefore do not have to be collapsed in any specific order) but prevents the containers from being collapsed as compactly as if the hinge line were nearer the base.
In the second approach, the hinge lines are staggered in distance from the base as compactly as permitted by the thicknesses and configurations of the sidewalls. In other words, the portion of the erected sidewall that is integrally molded onto the edge of the base is minimized. In the overlapped collapsed wall situation, the maximum overall compaction of the container normally occurs if the four collapsed sidewalls are effectively "stacked" on each other and the stack is directly against the base. To accomplish this, the four hinge lines are typically spaced from the base in increments of approximately the thickness of the sidewalls, each of the four hinge lines being progressively further from the base. The tradeoff in this design is that the walls must be collapsed in the specific order in which the hinges are positioned, in order to accomplish the desired "stacking" result (or sometimes even to permit all four of the walls to be collapsed at all). This can make the collapsing process relatively more complicated and slower than in designs in which the walls can be collapsed in any order.
This latter problem is somewhat reduced in designs such as the aforementioned U.S. Pat. No. 4,917,255 because one pair of opposing walls interfits with the other pair such that it is easy for users to see that the first pair must be released and collapsed before the other pair. In that patent, for example, the walls 16 and 18 in its FIG. 1 must be released from their engagement at the corners and then collapsed before the walls 20 and 22 can be collapsed on top of them (see FIG. 14 of that patent similar to FIG. 2 in this application! for an illustration of all four sidewalls in a collapsed condition). Even the type of design in U.S. Pat. No. 4,917,255 requires, however, that a specific wall of each opposing pair be lowered before the other of the pair (thus, in FIG. 1 of the foregoing patent, wall 16 must be lowered before wall 18, and wall 20 before wall 22). This is conveniently described as sequential folding. Although sequential folding maximizes the return ratio for a given configuration of container, sequential folding requires more concentration and effort to manipulate the container into its collapsed condition, and is therefore less efficient in assembly-line processes (and can even be more time-consuming to collapse) than containers in which there is no wall overlap.
If the sidewalls are not collapsed in the precise order required, the containers (including their hinges and other components) can be damaged by assembly line workers who sometimes try to force the sidewall members flat against the base member.
Another drawback of the sequential folding approach is that, in order to provide a container with a uniformly tall top edge when the sidewalls are erect, each sidewall member must be manufactured to its own specific dimensions. In other words, each sidewall member will be a different height and shape than the other sidewall members, because of the four different distances between the hinge pins and the top edge of the erect container. This requires additional investment in manufacturing capacity (for example, four separate sidewall molds must be built and used for injection molded, blow-molded and similar embodiments) and in inventory and distribution (again, four different types of sidewalls must be inventoried and controlled for distribution, assembly, replacement and repair).
Other applications and devices employing hinges or hinged members are similarly limited by the relatively fixed position of the pivot axis of the hinge. Negative effects (such as the need for sequential folding, a reduced return ratio, or the like) result from this limitation.